docker: Minimize Debian Jessie image

misc/docker/debian-jessie/Dockerfile

@@ -4,26 +4,23 @@ MAINTAINER Florian Bruhin <me@the-compiler.org>
 ENV DEBIAN_FRONTEND=noninteractive
 
 RUN apt-get -y update && \
+    apt-get -y dist-upgrade && \
     apt-get -y install python3-pyqt5 python3-pyqt5.qtwebkit python-tox \
-                       python3-sip python3-dev xvfb git dbus \
-                       python3-setuptools wget xinit build-essential \
-                       xserver-xorg-core xserver-xorg-video-dummy herbstluftwm
-RUN dbus-uuidgen --ensure
-RUN wget http://www.karlrunge.com/x11vnc/Xdummy -O /usr/local/bin/Xdummy && \
-    chmod +x /usr/local/bin/Xdummy
-RUN Xdummy -install
-# Keep image small after Xdummy is installed
-RUN apt-get -y purge build-essential && apt-get -y autoremove
+                       python3-sip xvfb git python3-setuptools wget \
+                       herbstluftwm locales
+RUN echo 'en_US.UTF-8 UTF-8' > /etc/locale.gen && locale-gen
 
 RUN useradd user && mkdir /home/user && chown -R user:users /home/user
 USER user
 WORKDIR /home/user
 
-RUN echo 'exec herbstluftwm' > /home/user/.xinitrc
-
 ENV DISPLAY=:0
+ENV LC_ALL=en_US.UTF-8
+ENV LANG=en_US.UTF-8
 
-CMD startx -- /usr/local/bin/Xdummy :0 & \
+CMD Xvfb -screen 0 800x600x24 :0 & \
+    sleep 2 && \
+    herbstluftwm & \
     git clone /outside qutebrowser.git && \
     cd qutebrowser.git && \
     tox -e py34